Electric machine



Dec. 26, 1933. F. LJUNGSTROM 1,941,038

ELECTRIC MACHINE Filed March 3, 1932 3 Sheets-Sheet l INVENTOR I 5M M MWZJQW ATTORNEYS.

Dec. 26, 1933. F. LJUNGSTROM 1,941,038

' ELECTRI C MACHINE Filed March 3, 1932 3 Sheets-Sheet 2 INVENTOR 5 a o ATTORNEYS Dec. 26, 1933. F. LJUNGSTROM 1,941,033

ELECTRIC MACHINE Filed March 3, 1932 3 Sheets-Sheet 3 F 5 12 6 Fi .1

[Hm IIIIID llil 5 3 Z 3 2 5 INVENTOR ATTORN EYS r Patented Dec. 26, 1933 I I L; I V v WUNIT DI S ATES P ENT OFFICE o TQ IEL G'mr MACHINE Y I Fredrik Ljungs'triim, Lidingo-Brevik, Sweden, as! g or to "Aktiebolaget Spontan, Stockholm, Swedemacorporationof Sweden N APlfl Qation'March 3.11932,seriammssassaansi o in SwedenMa -cli 5, 1931 ..-13Claims.' (01.171-252) =1he present invention relates ,to electric ma- It is an object of the present invention to chines, and particularly to synchronous alterovercome the-foregoing disadvantages and to nating current machines of the type operating maintain an exact centering betweenthedifierat relatively high speed. and employing arotor ent partsof the rotor by means that are unaf- 5 which includes arotatingimagnethavingwind fected by centrifugal force (and ,variations;in ings around the magnetic field. It is a-n object temperature; To thisend, the diif erent parts, of

of thisinvention to improve the rotor -:construc- :the rotor, as the magneticbody, the .non-magtion in such machines. 7 i j netic, intermediate members andtheshaft; trun- In machines of the type characterized, parnions, are maintained in proper relation to'each 10 ticularly of relatively. great, output and; high v otherandthe axis of rotation by .matinggrooves 65 speed of rotationas for, instance machines of and projections, such as ribs, keys, or the like, from 5,000 to 50,000 kw ,output rotating at 3,000 said grooves and projections being preferably R. P M., relatively high stresses due to centrifua. straight and lying inplanes whichintersect at or ,1 gal force tend tocause deformation of the rotor adjacentto the axis of rotation. In a bipolar body and vary its radial dimensions. ,Furtherrotor for example, the grooves and projectionsf more, in large rotors considerable variations in preferably extend perpendicularly to each other, dimensions occur :due to temperature changes, one set being arrangedparallel to the vvindingsi.-,v the rotor expan'ding under; high loaddue to in and the other being symmetrically arranged I creased, heat generation; while. at the sametirne transversely to the end surface of the poles. In the rotor is ,subject to irregular internal defor; multipolar rotors, asin a four pole rotor for ex- -75 mationdue to variations of temperature occur 7, ample, the number of grooves and projections ring in the core and the pole shoes-. The foremay be, so selected that they are arranged symgoing tends to varynotonly'the size of the rotor metrically mane end surfaces ofthe poleswhile but also its regularity, dependent'upon the load allowingradial expansion of the poles due to vcen- 2 and the length; of time duringwhichtherotor-is trifugal-force or heating effects. 7 v y subjected to the varying heating efiectsand o en- The invention is .capable of receiving trifugal'stre'sses. u ieW, e h l xp essions, some of hich vIt has heretofore-beenprmoosedto secure the are shown inthe accompanying drawings, but it shaft trunnions to.themagnet,body proper by a is. to be expressly understood that t d aw gs f circle" of screw bolts and to employ concentric are, forpm' Q i of illustration only and are not groovesand ribs on;- the .-.trunnions and magnet. tobe construed as a definition .ofthe limits of body to centerfthe one with respectto, the other. the invention. u V V H I These centering, means, however, are also afi'ect- .In said drawings, wherein the same reference ed .,by the deformation of the ,rotor. under the" numerals,indicate-corresponding parts in the action of centrifugal force and the heating effects; several flgures: i: o i I r A It is also usual to arrange between the shaft Figs; lto .5 inclusive show a bipolar rotor emtrunnion and the magnet body adisc or other bodyir g tlr e present invention, Fig. lb'eingan 1. member of. non -magnetic 'materialto' prevent evation of the rotor, Fig.2 being in' part a sec-; magnetic leakage between the magnetpoles, of tion .ofgan- .end,portion of the rotor on a larger.

40 the rotor, and such a member is subject todescale, FigsMB and flbein endviews of the:magformation under centrifugal stress and the heat net body and the intermediate member, and Fig, ing effects When this intermediate member fi jbeing a fragmentary section illustrating the is made of metal its coefficient of heat expansion relative arrangement of the grooves and projec-,- isjmuch greater than that of the steel in the mag: 'tions, i 3 V net body and the shaft trunnion, andfits co- 7 Figs. 6 to 11 are fragmentary views illustrat- 1 0 eflicientof elasticity is also greater, so that there ing someof the various arrangements of grooves is a tendency for the intermediate member to ,and projections; that maybe employed in conexpand more than the magnetlbody and the shaft formity with the present invention. 5

inclusive isa trunnion under the actionof heat. and centrifu- The rotorlshownin Figs-lto 5 gal force. These. deformations under centrifuf bipolarjturbo rotor muuamga agna body, 2, 105

gal force. and'the heating effects tend to ,ca'usef two nonamagnetieintermediate"members in th play between the surfaces1provided"for'.center- Lformpf plates 3 andj 'fh'arid shaft trunnions '5 in'gith'e parts and time may. result in a loos and 6, 'saidparts being? secured in"pos ition by ness or j oficentei" relationship. that is productive j screw. bolts" 7. Ihe rotorisf's'hown as" provided of strong vibrations; L h o I I withfso-called' 'singlegplaneiwindingsian; has 11o.

magnet core extend perpendicularly to the transverse winding grooves at the ends of the rotor,

and therefore tend on rotationv to expand at right angles to said grooves. V

In conformity with the present invention the magnet body is provided with grooves 13 and '14 1 extending perpendicularly to the winding grooves;

and receiving corresponding projections, here shown as integral ribs, provided on each intermediate member 3. Thereby'the rotor body and its pole shoes may assume different radial dimensions with respect to each intermediate member 3 by relative movement between .the grooves and projections. The intermediate member 3 is also provided with a groove 15 extending parallel to the winding grooves, and therefore at 0 right angles to grooves 13 and 14, and groove 15 receives a corresponding projection from the magnet core, thereby permitting relative radial movement and-adjustment in this-latter direction without interfering with exact centering. Similarly, each shaft trunnion 5- and the corresponding intermediate member 3 are provided with intersecting grooves and projections 16 and 17, which also permit relative radial movement and adjustment without interfering with exacto'centering. It will be observed that theforegoing arrangement is especially applicable to bipolar rotors, asin this case, with the diametric arrangementof the pole shoes 11 and 12 and their overhung relation to the pole core 8, said 'pole shoes may assume an oval shape in response to centrifugalforce without interference from the-intereng'aging ribs and projections Hand 14. In each of Figs. 6 to 11 inclusive the magnet body is designated 2, the intermediate member-3 and the shaft trunnion 5, and these figures illustrate some'jof the various ways in which the invention may be embodied. Whereas the embodimentof Fig. 5 shows integral ribs, Figs. 6 and 7 5illustrate theemployment of round andflat keys respectively-Fig. 8-being afractional sectional elevation illustrating the employment of-keys.

Figs. 9 and 11 illustrate the employment'of -alplurality of ribs or, keys extending parallel 'to the winding grooves, and any suitable number of such'projections can be employed, the figures indicating one between each pair of grooves.

As shown in these figures the projections -may beformed upon either of the coacting members and extend into grooves formed in'the otherof said -members. Where only one projection extends in each of the two right angular directions, their planes preferably intersect at'or closely ad- ,jacent the axis of rotation. Where a plurality 'or 50para1lel projections are used in one or both of the right angular directions, they are preferably arranged symmetrically and the planes of two right angularly disposed projections prefer- .ably intersect at or closely adjacent to the cen- 5 ter of rotation.

It will therefore be perceived that by the presentinvention the members of the'rotor are so centered with relation to eachother that, changes of radial dimension, by reasonof either or both "centrifugal force and thelheating effects, are not productive of deformation} of the centering means orthe development of playand looseness between the parts becauseofrepeatedchanges of radialdimension. While the invention has been 7 describedand illustrated wth"'reference to cer-' a rotor which includes a rotating magnet and windings placed around the magnetic field, the combination of a rotorbody, a trunnion, an intermediate member, and-cooperating grooves and projections for centering said body and member while permitting relative radial movement therebetween, said cooperating grooves and projections lying in directions which intersect at or adjacent to the axis'of rotation.

2. In electric machines, particularly synchronously alternating current machines, of'the type operating at relatively high speed and comprising a rotor which includes a rotating magnet and windings placedaround the magnetic field, the combination of a rotor body, a shaft trunnion, and cooperating grooves and projections for centering said body and trunnion while permitting i relative radial movement therebetween, said 00- operating grooves and projections lying in directions which intersect at or adjacent to the axis of rotation.

3.- In electric machines, particularly synchronously alternating current machines, of the type operating at relatively high speed and comprising a rotor which includes a rotating magnet and windings placed around the magnetic field, the

combination of a rotor body, a shaft trunnion, an intermediate member, and cooperating grooves and projections on said body and member and -on said member and trunnion for centering the same while permitting relative radial movement therebetween,said cooperating grooves and projections lying in directions which intersect at or adjacent to the axis of rotation.

4. In electric machines, particularlysynchronously altematingcurrent machines, of the type operating at relatively high speed, the combinar25 'tion of a rotor body, an'element cooperating therewith, and coacting'grooves and projections on said body and element for centering the same relatively to each other while permitting-relative radial movement, said coacting grooves and projections being straight and angles to each other.

5. In electric machines, particularly synchronously alternating current machines, ofthe type operating at relatively high speed, the combina extending at right tion of arotor body, an element cooperatingtherewith, and coacting grooves and projections on said body and element forcentering the same relatively to each other while permitting relative radialmovement, said cooperating grooves and projections being symmetrically arrangedand disposed in-lines which intersect 6. In electric machines, particularly synchronously alternating current machines, of the type operating at relatively high speed, the combinarelatively to each other 'whileperniitting relative} radial movement, said coacting grboves and pro-" 1',941,oss jections being straight and extending at mm 1 angles to each other and being disposed'in lines tions being disposed in lines which intersect at or adjacent to the. axis of rotation of said rotor] body.

'8. In electric machines, particularly synchronously alternating current machines, of the type operating at relatively high speed, the combination of a rotor body, a shaft trunnion, an interi mediate member, and coacting grooves and projections on said body, intermediate member and shaft trunnion for centering the same relatively to each other while permitting relative radial movement, said coacting grooves and pronously alternating current machines, of the type' operating at relatively high speed, the combinaradial movement, said cooperating grooves and jections extending at right'angles to each other.

9. In electric machines, particularly synchrotion of a rotor body, a shaft trunnion, an intermediate member, and coacting grooves and projections on said body, intermediate .member and shaft trunnion for centering the same relatively to each other while permitting relative projections being arranged insymmetrically ar ranged intersecting planes.

10. Inelectric machines, particularly synchronously alternating current machines, of the type operating at relatively high speed, the combination of a rotor body, a shaft trunnion, an intermediate member, and coacting grooves and projections on said body, intermediate member and shaft trunnion for centering the same relaintersect at or adjacent to 'of said rotor body.

tively to each other while permittin g relative radial movement, said coactlnggrooves and projection's being straight and being disposed in lineswhich intersect at or adjacent to the axis of.

rotation of said rotor body.

11. In electric'machines, particularly synchro nously alternating current machines} of the type operating at relatively high speed, the combination of ,a rotor body, a shaft trunnion, an intermediate'member, andcoacting grooves and projections on said body, intermediate member and shaft trunnion for centering the same relatively to each other while permitting relative radial movement, said cooperating grooves and projections being symmetrically arranged and at' least two of them being arranged in planes which 12. In electric machines, artieuianysy'nchm nously, alternating current machines, of the'type operating atirelatively high speed, the combination of, a rotor body, an element cooperating, therewith, andcoacting grooves and projections on said body and element for centering the same.

relativelyto each other while permitting relative radial movement, a plurality of said grooves and projections being parallel and disposed at an angle to another of said grooves and projections;

13. In electric machines, particularly synchronously alternating current machines, of the type operating at relatively high speed and comprising arotor which includes a rotating magnet and windings placed around. themagnetic field,

the combination of a rotor body, an element cooperating therewith, and coacting grooves and the axis of rotation projectionson said body and element. for centeringthe same relatively to each otherwhile permitting relative radial movement, at least one 'of aid coacting grooves and projections extending at right angles to said windings and'another of said coacting grooves and projectionsextending, parallel 'to said windings.

' FREDRIK JUN sTRoM. 

